Spin – This setting applies modulation to the early reflections with an X-Y controller. Sliding the controller to the left and right affects the depth of modulation, while sliding up and down affects the amount.
Slide the Spin’s contoller all the way to the top right.
This puts the spin effect at full.
Play a note for a truly bizarre sound.
These early reflections are being modulated by a low frequency sine wave, which creates the warbly effect you’re hearing.